Metro tunnel boring starts
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Chennai: The fears of George Town, Chintadripet and Shenoy Nagar residents have been proved groundless. The TBMs (tunnel-boring machines) of Chennai Metro Rail (CMRL) are roaring beneath their houses without their even feeling it.
Senior CMRL officials, who confirmed that boring work was under progress in these areas, told Deccan Chronicle that the machines have dug nearly 400 metres in Washermanpet area alone. The first TBM has dredged over 280 rings (each ring measuring 1.4 metres) and the second machine has tunnelled 93 metres in Washermanpet.
The two TBMs in Nehru Park, from where the first TBM of CMRL set rolling, has dredged 283 rings and 135 rings (1.2 metres) respectively. May Day Park, where dredging began most recently, has covered 16 rings (each 1.5 metres). Five of the 11 TBMs shipped from abroad for the underground sector are in motion.
Of the 24 km underground stretch of the entire 45 km metro rail network, TBMs would run beneath 240 structures in Mannadi, 110 in Chintadripet and 53 in Shenoy Nagar, an official added.
However, tunnel boring ran into trouble at Seven Wells last week when concrete poured from overground for metro work seeped into a borewell falling within its route, littering the interior of a nearby shop. Blaming the shop-owner for failing to inform them about the presence of the borewell, CMRL officials said, if informed, the borewell could have been closed like others and necessary compensation paid to him. In this case, the shop-owner was not aware of a borewell in his shop. CMRL identified and closed 397 borewells and 57 open wells falling within its route.
There was no reason to fear as tunneling takes place 9 metres beneath the surface, officials reasoned, adding that protective girders and diaphragm walls would keep the tunnel in tact. Also, the TBMs are fully automated and the machine adjusts speed by factoring in the soil nature.
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